In the cases in which the contents of speech greatly affect the company image, such as operation services by a telephone and over-the-counter services at a bank or the like, quantitative speech evaluation is important for improvement in the quality of the contents of speech.
As one of indexes for quantitatively carrying out speech evaluation, the inflection of speech voice exists. The magnitude of the inflection of speech voice may be quantified as time change of the tone height of the voice.
As a technique for extracting the time change of the tone height of voice, a pitch estimation technique exists. The pitch estimation technique is a technique for detecting a peak of a voice spectrum in the case in which a voice waveform is transformed to the frequency domain based on the correlation between one section and another section in the voice waveform. As the pitch estimation technique, Masanori Morise, “Knowledge Base,” the Institute of Electronics, Information and Communication Engineers, pp. 1-5, 2010, has been disclosed, for example.